Heat exchanger



Aug. 28, 1951 J. w. BROWN, JR 2,565,161 HEAT EXCHANGER A Filed Feb. 15,1946 2 Sheets-Sheet 1 INVENTOR. JO/ N M 520w JR,

Jaw/M Patented Aug. 28, 1951 UNITED STATES PATENT OFFICE HEAT EXCHANGERJohn W. Brown, Jr., Lakewood, Ohio, assignor to Brown Fintubc Company,Elyria, Ohio, at corporation of Ohio This invention relates to a heatexchanger and more particularly to a heat exchanger for use withcommodities having low co-eificients of heat transfer, for examplegases. Such commodities require extensive surface area in the heatexchanger element in order to obtain effective heat transfer and thisrequires a relatively large surface area in the path of the commodityflowing therethrough.

In the design of heat exchangers it has been determined that a veryefficient arrangement of extended surface for interchange of heatbetween the fluid and side walls or plates of the fluid conduitcomprises a series of parallel elements lying in the path of fluid flowand extending from one side wall to the other. Exchangers have beenbuilt in which this construction is embodied in a large number ofparallel spaced pin elements extending between the side walls. Aconstruction of this kind is illustrated and described in copendingapplication, Serial No. 638,348, filed December 29, 1945, in the namesof John W. Brown, J r., and Robert W. Kaase, and assigned to myassignee. The construction there shown possesses excellent heat transferefficiency and the pin-like elements perform the further function ofacting as tension members to reinforce the side walls of the conduit andprevent their being bulged outwardly by pressure of the commodity withinthem.

The present construction in some respects constitutes an improvement onthe exchanger disclosed in that application particularly with regard tothe nature of the bond formed between the side walls or plates and thepin-like elements and the manner in which the elements are formed.

A general object of the invention is the provision of an extremelyefficient heat exchanger of the type embodying elements with the formand heat transfer characteristics of pin-like members, and that issimple to construct, economical to manufacture and of improved strength.A further object is the provision of a heat exchanger in which thepin-like elements are provided in extruded or rolled metal strips, anumber of which may be assembled together to form a heat exchangerpacking. Another object of the present invention is to provide a heatexchanger in which the pin-like elements comprise a series of flat finsmounted substantially normal to the side walls in efiicient heatconducting relation therewith and are bonded thereto. Still anotherobject of the invention is to provide a construction in which thepin-like elements or fins are positioned with a high degree of accuracywith respect to each other so that they may be staggered to divert thefluid to new paths as it flows through the exchanger and thus to insureturbulent flow and improve the efficiency of heat transfer. Anadditional object of the invention is to provide a construction in whichsuccessive sheets are positioned with respect to each other to form withthe adjacent side walls a series of interstices to receive and hold themolten bonding material that subsequently hardens to retain theexchanger together, and thus prevent the bonding material from coatingthe pin-like elements. Another object is the provision of a constructionwhich may be adapted to provide pin-like elements or fins of manydifferent types and arrangements, so that the most efficient design maybe selected for the ducts for which the exchanger is designed.

Further objects and advantages of the invention will become apparentfrom the following description of a preferred form thereof, referencebeing made to the accompanying drawing. The essential characteristicsare summarized in the claims.

Referring now to the drawings: Figure 1 is a perspective viewillustrating the exterior appearance of one type of heat exchanger madeaccording to the present invention; Figures 2.and 3 are sections throughthe heat exchanger of Figure 1 as indicated by the lines 2-2 and 33thereon, the arrows of Fig. 3 showing concurrent flow; Figure 3a is adetail section as indicated by lines 3a3a in Figure 3; Figure 4 is anend elevation of a single extruded packing sheet in which the pin-likeelements are formed; Figure 5 is an end elevation of a modified form ofpacking sheet made from sheet stock folded along opposite edges; Figure6 is a side elevation of the sheet of Figure 4 showing two'shapes offluid passages formed therein, one on each side of a break line; Figure7 is a section through Figure 5 as indicated by the line 1-1 thereonshowing the construction of one form of offset fins by choiceillustrated with a. rolled sheet member; Figure 8 isa section similar toFigure 7 showing a modified form of offset fin construction; Figure 9 isa section through Figure 4 as indicated by lines 9-! thereon showing afurther modification with the fins formed in an extruded sheet member soas to lie flat in the plane of the sheet; and Figure 10 is a fragmentarysection as indicated by lines Ill-Ill in Figure 2, but enlarged to showthe nature of the bond between the sheets and the side walls andillustrating on opposite inlet l6 and discharged at an outlet sides of abreak line the sheet constructions of both Figures 4 and 5. It is to benoted that the taking of sections for Figures 7 and 8 through Figure 5and Figure 9 through Figure 4 is only for convenience in utilizing aminimum of figures. Any of the fin constructions of Figures '7, 8 and 9may be used with the type of sheet shown in either Figure 4 or Figure 5.

The preferred form of heat exchanger embodied in this invention is of atype wherein the commodity, as a fluid, flows between conduit side wallsin the form of flat plates arranged to provide separate and contiguouspassages so that two or more fluids may be passed through the devicewhile separated from eacir other by the plates. To effect rapid andefficient transfer of heat from one fluid through the intervening sidewall plate to the other fluid, the space between the plates and in thepath ofeach commodity is filled with a heat conducting packing ormatting. As the fluid flows through the packing the desired heatt'ransfentakes place. In effect, this packing constitutes alarge numberof accurately spaced pin-like tension elements, hereinafter called fins,extending between the side walls and bonded to them to provide foreflicient heat transfer to the side walls as-well as for thereinforcement of the entire structure.

In the preferred form of the invention the flns are formed in stripswhich are preferably extruded and are of a flat cross section withbeaded or bulbous edges. The bulbous edges hold adjacent strips at apredetermined distance from each other and also stiffen them. In amodified construction a similar result is obtained by forming flatstrips with bent over edges to increase the effective thickness at theedges and also to stiffen it. As indicated from the drawings the finsthemselves may be formed and shaped in different ways although in eachcase they are preferably formed in the strip by a blanking operationthat provides passages through the strip for the commodity and producesthe pin-like effect. Also, the fins preferably extend transversely ofthe strip from closely adjacent one edge thereof to closely adjacent theother in order that they may act as tension elements to reinforce theside walls to which the edges of the strip are bonded. The fins may bebent or offset from the general plane of the strip or they may be leftparallel with and in the plane of the strip. The openings may takevarious shapes, although they are preferably elongate, and the ratio ofopening to fln can be varied to suit the requirements of the service forwhich the exchanger is intended.

A heat exchanger constructed in accordance with the present invention isshown in Figures 1, 2 and 3. Such an exchanger may comprise a plurality,in the present case four, of substantially parallel fluid passages orconduits- In, II, I! and I3. The passages I and 12 are incom municationwith a suitable inlet l4 and outlet l to permit passage of one fluidtherethrough. In like fashion the other commodity passing throughconduits II and I3 is admitted at an It will .be noted from Figure 1that the arrangement described provides for counterflow of the fluidswithin the respective chambers although it will be apparent thatconcurrent flow can be provided if desired as shown in Fig. 3.

The conduits or chambers H), H, I2 and I3 are made up of nested, shallowchannels or pans 20, 2|, 22 and 23 respectively. The bottoms of thechannels 2|, 22 and 23 act as side walls to separate the chambers orconduits I0 and II, II and I2, and I2 and [3, respectively. The bottomof the channel 20 has no heat exchange function inasmuch as only oneface of it forms part of a conduit. The conduit I3 is closed by a plate24 that conforms in shape to the bottom of a channel but has onlysufficient side wall to permit it to nest properly in the vertical ,wallof the channel 23. The manner in which the nesting of the channels andthe plate 24 is accomplished is illustrated in Figure 3 showing thevertical walls of the several chambers that are formed by flanges 26,21, 28 and 29 respectively. These flanges are formed at each of twoopposite ends of the channel bottoms and are deformed outwardly adjacenttheir edges as indicated at 33 to receive telescopically the bottom ofthe adjacent nesting channel. In the case of the chan nel 23 the outwarddeformation 33 is to permit reception of the top plate 24.

All of the channels and the plate 24 are brazed or soldered togetherafter assembly, preferably by the method disclosed in my copendingapplication referred to above.

End walls for the conduits may be provided by suitable plates 31 brazedor soldered in place. The fluid inlets and outlets extend through theapertures in the respective flanges as shown in Figures 1 and 2 and maybe secured in place by brazing, soldering or other convenient means.

Packing is placed in the conduits In, H, l2 and I3 and bonded to theconduit side walls to act as a heat transfer medium between thecommodity and the side walls. The packing includes a large number offins that are straight and bonded to the side walls to provide extendedheat exchanging surfaces and to serve as tension members that reinforcethe heat exchanger structure against fluid pressures within the conduit.

The packing fills almost all of the interior. of a conduit except aspace at each end, across the exchanger, and adjacent the inlets l4 andI6 and the outlets l5 and H. This space is occupied by channel shapedmembers 38 mounted one against the other with their flanges lying alongand bonded to .the walls of the conduits and their bases normal thereto.The bases are provided with a series of large holes 39 to permit freefiow of a commodity therethrough, and serve as tension members toprevent outward bulging of the conduit side walls due to pressuredeveloped within the conduit. The channels also function to permit thecommodity to distribute itself across the packing at each end as itflows through from an inlet to an outlet and thus insure effectiveutilization of all sections of the packing.

As noted above, packing that is used as a medium of heat exchangebetween the commodity and conduit sidewalls comprises a series of metalstrips, preferably formed by extrusion, but not limited to such methodof fabrication; and

stacked face to face inside of each of the conduits III, II, I2 and I3.The strips are so positioned that they extend up and down as shown inFigure 2 andlie substantially parallel to each other in planes normal tothe walls of the conduits.

The preferred cross sectional form of sheet results from extruding astrip 40 with a cross section as shown in Figure 4 having a trim, flatcentral portion 4| and bulbous or beaded edges 42. In addition to thispreferred form of'construction other forms such as that shown in Figure5 may be employed. In this figure there is shown a flat strip 43 turnedover and doubled back on itself at opposite edges 44 to form aconstruction in cross section'approximating the construction shown inFigure 4. The enlargements at the edges of the strips automaticallyspace them at the proper distance from each other for the mostadvantageous fluid flow and heat transfer conditions when assembled. Theenlarged edges also serve to stiffen or reinforce the individual strips.

In order to provide the required pin-like heat conducting fins, andinsure turbulence of flow,

openings as shown in Figures 6, 7, 8 and 9 are provided. In Figure 6 twokinds of elongate openings are shown; one type, at the left, having theform of an elongate oval as shown at 45. The other type, at the right,is of rectangular shape and is indicated at 46. In each case theopenings (either 45 or 46) leave between them a series of spacedpin-like sections or fins 48 that extend from one edge to the other ofthe sheet and are bonded at their ends through the edge portions toconduit walls, as 20 and II, to reinforce the same against the pressureof fluid within the conduit. So long as the sheet construction embodies,in accordance with heat exchanger requirements, the formation of anadequate number of such tension elements to withstand the internalpressures, the shape and size of the out out openings 45 and 46 are notcritical.

There is an advantage from the heat transfer standpoint in the use ofthe oval openings 45 with commodities such as steam having a highcoefl'icient of heat transfer. This is because a thicker section of finadjacent the outer edges of the strip, which section is indicated at 50,will permit more efficient transfer of heat from the central portion ofthe fin as indicated at 52. With other commodities having lowcoefiicients of heat transfer, area considerations are more importantthan the capacity of the fins to transmit heat, and straight openingsare then preferred. Considerations of heat exchanger efficiency andpressure drop in the fiuid govern the spacing of fins-and relative sizeof the parts.

It is frequently desirable to position the fins 48 so that they lie inthe plane of the strip as shown in Figure 9. On the other hand it issometimes desirable to bend the fins as shown in Figures 7 and 8 toprovide a diverting passage for the fluid, causing it to travellaterally with respect to the sheets. In Figure '7 the fin 48a includesa tongue 55 struck outwardly from the plane of the strip leaving anopening 58. The tongue remains joined to the strip by a portion 59 ofthe fin 48a that remains unbent and that acts as the tension memberextending from one edge of the strip to the other.

Another bent type of fin'is illustrated in Figure 8. In this figureelongate openings 60 are formed in the sheet stock 62 between fins 48b.The fins are then bent out of the plane of the strip as shown in thatfigure although their entire cross section remains joined at the ends tothat material adjacent the strip edges; thus the cross section of thefins is uniform throughout and the fins are not weakened nor their heattransfer capacity diminished at the juncture of the fins with the edgesof the strip. It is preferable in both of these modifications, however,that the amount the fins are bent out of the plane of the strip shall beno greater than that permissible without interference between the finsof the one strip and any part of the adjacent strips between which it ispacked.

The fins lie in the plane of the sheet in the construction of Figure 9,and are indicated at 8 480 while the spaces between them are shown at54.

The strips described above are assembled in units in respective conduitsI0, II, I! and II. The conduit l0 bounded by side walls 1:0 and II ispartially shown in Figure 10. In this figure the extruded strip ofFigure 4 and bent strip of Figure 5 are each shown bonded in place, oneexample being shown on each side of the break lines of the figures. Innormal use a packing will be made up of only one kind of strip.

In each case it will be seen that the thickened edges of the strips notonly space them properly, but also provide interstices 58 between theadjacent rounded edge surfaces and conduit side wall 20 or 2|. Thesurfaces of the rounded bulbous edge or the Figure 4 construction andthe rounded bent construction of Figure 5 each form these interstices.Their function is an important one in that they each provide a longtubular opening of somewhat triangular cross section to receive and holdmolten solder or other bonding material during the assembly operation.

At the time of assembly solder is interposed in sheets between sidewalls2i and 2| respectively and the assembly of packing members therebetween.Then, as pressure and heat are applied the solder melts and is held bycapillary attraction adjacent the surfaces which are to be bondedtogether. An excess of solder is ordinarily supplied in order to insurethat sufficient solder will be present, to create the required bond. Theexcess is retained between the contacting parts of adjacent stripspreventing the solder from running ofi. Thus the fins remainsubstantially free from solder, and the possibility of solder cloggingor restricting the openings is eliminated. While it is molten and as ithardens the solder is held in place and made available to complete afirm bond between sheet 20 or II and the packing members on each side ofthe respective interstices. Since these bonds and the bonds of the endmembers 38- extend over substantially the entire inner surface of theside walls 20 and 2| the packing members and end members are integrallybonded thereto as a unitary assembly. The bonds provide ample mechanicalstrength to withstand forces imposed thereon by fluid pressures withinthe conduits.

Various other changes and modifications may be made without departingfrom the spirit and scope of my invention. It is therefore to beunderstood that my patent is not limited to the preferred forms of theinvention described herein, or in any manner other than by the scope ofthe appended claims.

I claim:

1. In a heat exchanger unit, the sub-combination comprising two sidewalls and, extending from one to the other thereof, a heat conductingpacking made from a plurality of substantially contiguous individualmembers each bonded thereto and comprising a long and relatively narrowstrip of metal shaped to be substantially thicker along opposite edgesand for a substantial distance inwardly than at its midportion andprovided with a plurality of elongate pin-like heat transferring finsformed integrally with the strip and extending from adjacent one of saidopposite edges to adjacent the other edge, said members abutting mainlyalong the thick portions characterizing their opposite edges and beingout of contact between such thick portions.

2. In a heat exchanger unit, the sub-combination comprising two sidewalls and, extending from one to the other thereof, a heat conductingpacking made from a plurality of substantially contiguous individualmembers each bonded thereto and comprising a lon and relatively narrowmetal strip shaped to be sub stantially thicker along its long edges andfor a substantial distance inwardly than at its midportion and providedwith a plurality of elongate heat transferring fins separated byelongate openings extending from adjacent one long edge to adjacent theother long edge to act as fluid passages for a commodity passed throughsaid exchanger, said members abutting mainly along the thick portionscharacterizing their oppositeedges and being out of contact between suchthick portions.

3. In a heat exchanger unit, the sub-combination comprising a heatconducting packing made from a plurality of stacked substantiallycontiguous individual members, each comprising a long and relativelynarrow metal strip provided with a series of fins struck from the flatstrip surface and bent outwardly therefrom and integrai spacer meanstaking the form of opposite portions extending continuously alongopposite edges of said strips to space said fins from the next adjacentmember, theindividual members making up the packing being stacked withtheir enlarged portions in abutting relation to each other;

4. A heat exchanger comprising a closed structure having a pair ofopposed side walls, inlet and outlet means communicating with the spacebetween said side walls, a heat conducting packing between said sidewalls and extending from one to the other, said packing comprising apinrality of substantially contiguous individual metal strips abuttingeach other only at their edges each of which strips is formed with aseries of oiiset fins separated from each other by openings extendingtransversely of said side walls continuously from adjacent one wall toadjacent the other wall to provide fluid passages for a commodity passedthrough said exchanger, and a metallic bond between said strips and saidplates to provide a heat conducting assembly.

5. A heat exchanger comprising a closed structure having a pair ofopposed side walls, inlet and outlet means communicating with the spacebetween said side walls, a heat conducting packing between said sidewalls and extending from one to the other, said packing comprising aplurality of individual metal strips with rounded edges in abuttingrelation to each other each of which strips has a plurality ofintegrally formed heat conducting fins separated by openings acting asfluid passages for a commodity to be passed through said exchanger, anda bond formed of heat conducting bonding material to provide a heatconducting unitary assembly 01 said side wall and said strips.

. JOHN W. BROWN, Jn.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Great Britain Dec. 20, 1937

